Outcome predictors in patients with normal pressure hydrocephalus]

Despite the accumulation of knowledge over the years, the postoperative results of shunt implantation in patients with normal pressure hydrocephalus (NPH) have shown little improvement. This means that reliable predictors of the course of the disease need to be identified. In a prospective study carried out between 1982 and 2000 we re-examined 155 (78%) of 200 NPH patients treated by shunt implantation, 7 months after their operation. On the basis of the results of the intrathecal infusion test NPH was graded early stage (no brain atrophy) or late stage (brain atrophy). We looked at the following factors as possible predictors: patient's age, disease duration, idiopathic or secondary aetiology, clinical signs such as gait ataxia, dementia and urinary incontinence, results of spinal tap, valve type and valve infection, and resistance to cerebral spinal fluid outflow and postoperative changes in ventricular size. As a measure for outcome we used the NPH recovery rate, and the Pearson chi-square test for statistical evaluation. 80 patients with early stage NPH, a history < 1 year, absence of dementia and an implanted Miethke dual-switch valve proved to be significant predictors of a positive outcome. Outflow resistance proved to have only minimal impact on outcome. The 75 patients with late-stage NPH had better outcome when dementia was absent, outflow resistance was > 20 mmHgmin/ml, the CSF tap test was positive, and a Miethke dual-switch valve was implanted.